This invention relates to apparatus and method for cleaning thin, disc-like wafers of material, and more particularly, a method and apparatus for thoroughly cleaning semiconductor materials prior to further processing. In the manufacture of semiconductor elements, the individual wafers are cut from a billet (elongated crystal) of material into very thin wafers which are ultimately cut into small pieces to form diodes and other electronic elements. After the wafers are cut from a billet, during which operation cutting lubricants are utilized, they are then lapped and polished. During such processes, the residual lubricant film, as well as particles of the semiconductor material removed by polishing, etc. remain on each surface of the wafer. These materials must be totally removed prior to further processing of the wafers. Typical wafer materials are silicon and germanium.
The scrubbing or cleaning of the wafers may be accomplished by placing each individual slice or wafer in a carrier which then moves or otherwise positions the wafer with respect to one or more scrubbing brushes and/or other cleaning mediums. The wafers so supported are generally indexed through a series of cleaning stations. Representative of prior art devices utilized to accomplish the above are the following U.S. Patents:
U.S. Pat No. 3,585,668; Jaccodine et al 6/2/69 PA1 3,664,872; Frank et al 5/23/72 PA1 3,691,694; Goetz et al 9/19/72 PA1 3,748,677; Frank et al 7/31/73 PA1 3,915,739; Maahs et al 10/28/75 PA1 3,921,796; Bok et al 11/25/75 PA1 3,939,514; Cook; 2/24/76 PA1 3,970,471; Bankes et al 7/20/76
Despite the existence of the above-indicated equipment, there still exists a need for a method and apparatus which can thoroughly scrub and otherwise clean all the surfaces of such wafers in a thorough, efficient manner while not needlessly exposing such wafers to flexure stresses as can be imparted thereto by movement into and out of contact with rotating brushes and the like. It is accordingly a primary object of the present invention to provide an apparatus and method for cleaning wafers of the type hereinunder consideration wherein the wafers are held in a unique manner so as to expose all the surfaces thereof as by a bracket capable of being indexed through a plurality of cleaning stations arranged in an arcuate path and then discharged therefrom in a condition which enables the thus treated wafers to be immediately further processed.
Another object of the present invention is the provision of an apparatus and method of cleaning wafers which is flexible enough in its manner of use that a large variety of types and sizes of wafers may be processed thereby in a straightforward and trouble-free manner conducive to low-cost operation.
A still further object of the present invention is the provision of an apparatus and method for cleaning wafers of the type hereinunder consideration to be subjected to minimal acceleration and flexure stresses during processing so as to enable such wafers to be processed with a minimum of breakage thereof.
A still further object of the present invention is the provision of an apparatus and method for conveying the wafers hereinunder consideration into and out of the processing path of the present invention. Accordingly, their handling during such processing as by machine operators or inspection equipment is both minimized and capable of essentially complete automation so as to present both completely cleaned and dried semiconductive wafers in a form immediately usable for further processing.
These and other objects of the present invention are accomplished by supporting the wafers to be cleaned in an upright generally vertical position. In such position, they are contacted preferably at two spaced locations at both their leading and trailing edges. Thereafter, the wafers are indexed through a plurality of cleaning stations. At least one of the cleaning stations includes a pair of generally parallel brushes mounted for rotation along axes parallel to each other and a plane passing through such travel path. The brushes may be moved to an open position to enable the wafers to be positioned therebetween and a closed position wherein the brushes simultaneously contact both sides of the wafer in a scrubbing action while the wafer is independently rotated so as to enable scrubbing action to reach all surfaces of the wafer. The path is in part defined by an arcuate track, in turn including means for independently rotating the wafer at the scrub stations. Furthermore, the brushes move so as to establish an operative relationship between the wafer and the independent means for rotating such. Additionally, a scrub rinse, a rinse, and a dry station may be additionally provided along the path and the path is appropriately interrupted at opposite ends thereof so as to enable the wafers to be serially moved thereto and removed therefrom.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.